Printed circuit board comprising electrical conductor paths and means for electro-optical and/or opto-electrical conversion

ABSTRACT

The invention relates to a printed circuit board comprising electrical conductor paths, said printed circuit board also being provided with optical conductor paths. Furthermore, electro-optical or opto-electrical means are provided on or in the printed circuit board.

CROSS REFERENCE TO RELATED APPLICATION

This application is the US National Stage of International ApplicationNo. PCT/DE2003/002729, filed Aug. 13, 2003 and claims the benefitthereof. The International Application claims the benefits of GermanPatent application No. 10241203.0 DE filed Sep. 5, 2002, both of theapplications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a printed circuit board according to thepreamble of the claims.

BACKGROUND OF THE INVENTION

As a result of the increasing miniaturization of electronics, theperformance capability of electronic components, modules and systems isimproving. In the area of data processing and data transmission, as wellas in telecommunications, this is finding expression in increasing clockrates and data rates. In specialist circles, it is assumed that theclock frequency of processors will rise from about 1 GHz in 1999 to over10 GHz in 2012/2014.

The performance capability of processors can only be utilized if theexternal connections enable the transmission and processing as well asthe switching, multiplexing and demultiplexing of these highfrequencies. Due to crosstalk, reflections and line losses, the demandsin terms of electrical construction and connection technology becomemore and more critical as frequency increases. Due to inadequateconnection technology, the potential of processors can often not beutilized.

New electrical solutions and concepts for this problem are associatedwith high costs.

As an alternative, optical components or devices are increasingly usedfor transmission. Electrical problems are avoided by means of theoptical technology.

Previously, these optical components or devices were mounted on printedcircuit boards. In this case, the optical components are connected bymeans of optical waveguides. The optical waveguides of one or moreprinted circuit boards are in this case connected to one another bymeans of splicing or optical connectors. They often lead to otherdiscretely constructed modules. These structures avoid electricalproblems, but are relatively time-consuming to construct and arecost-intensive.

SUMMARY OF THE INVENTION

The object of the present invention is to reveal a simple connectiontechnology for optical components.

This object is achieved in the printed circuit board according to theclaims.

Through the integration of electrical and optical connections orconductor paths on a printed circuit board, optical components ordevices of electrical circuits can easily be connected to one another.Likewise, optical circuits can be integrated and the power supply tooptical components or the control of optical components can beimplemented by means of electrical circuits on a printed circuit board.

Advantageous embodiments of the invention are specified in thesubclaims.

In one embodiment, the optical conductor paths or connections arefashioned as optical waveguides. This has the advantage of providingparticularly low-attenuation and low-distortion connections.

In a further embodiment, the printed circuit board is fashioned as amultilayer printed circuit board, i.e. it consists of a plurality oflayers. A layer can in each case contain electrical or opticalconnections. Mixed forms are also possible. The layers of electrical andoptical connections or conductor paths do not have to be alternating.There can also be a plurality of layers of one type which in turn lieabove a plurality of layers of the other type.

Here, the inner conductor paths can be reached by accesses at rightangles relative to the plane of the conductor paths. The conductor pathscan also be fashioned so as to lead through laterally.

The use of a multilayer printed circuit board has the advantage thatcomplex electrical and optical circuits can be integrated on one printedcircuit board.

In one embodiment of the invention, the optical components or devicesare integrated in the printed circuit board. This has the advantage thatintegrated optics are possible, i.e. for example,micro-electrical-mechanical systems, MEMS for short, which optionallyemit an optical signal at one of two outlets, are integrated. By thismeans, the advantages of the integrated optics can be combined with theadvantages of the electronics on the printed circuit board.

Through doping of the optical conductor paths, linear and non-linearoptical effects can be achieved, advantageously integrated on a printedcircuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be explained in detail belowand are represented in the drawings, in which

FIG. 1 shows a schematic representation of a printed circuit board withan electrical and an optical plane and an electro-optical device.

FIG. 2 shows an exemplary embodiment with a multilayer printed circuitboard.

FIG. 3 shows a further exemplary embodiment with a multilayer printedcircuit board which carries optical signals of differing wavelengths.

FIG. 4 shows a section for an embodiment of an optical layer in across-sectional representation showing perspective.

FIG. 5 shows a block diagram of an add/drop multiplexer.

FIG. 6 shows an internal structure of the add/drop multiplexer accordingto FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a printed circuit board LP. This consists of a base layer1, an optical layer 2 which has an optical conductor path 3, for examplean optical waveguide, an electrical layer 4 which is electricallyinsulating and has electrically conductive conductor paths 5. Anelectro-optical device 6 is connected to the electrical conductor paths,said electro-optical device 6 being arranged on a connecting opening 7to the optical layer 2. The optical side of the electro-optical device 6is effectively connected optically by means of an optical couplingelement 8, for example a mirror or micro-electrical-mechanical system,called MEMS for short, to the optical conductor path 3.

FIG. 2 shows an representation analogous to FIG. 1 with the differencethat further layers are shown. FIG. 2 shows two optical layers 2 and twoelectrical layers or planes 4 with conductor paths not shown, aconnecting opening 7 and an optical coupling element 8. The arrow 9,which leads from the optical conductor path 3 to the optical couplingelement 8, and the arrow 10, which leads outward from the opticalcoupling element 8, show schematically the path of a coupled ordecoupled optical signal.

By analogy with FIG. 2, FIG. 3 shows schematically a printed circuitboard with a plurality of layers, for example a multilayer board ormultilayer printed circuit board. Here, various optical signals, forexample of differing wavelength, are transmitted in the optical layers.

FIG. 4 shows a section of an embodiment of the optical layer 2. Here,this layer consists of a first sublayer T1 with a first refractive indexn1. Arranged above this is a second sublayer T2 with a second refractiveindex n2. This second sublayer has a light-conducting orlight-wave-guiding cross-sectional profile, and in the example this is araised rectangular channel. Arranged on the sublayer 2 is a furthersublayer 3 with a third refractive index n3. In general, the refractiveindex of the central sublayer T2 has to be greater than that of thelower or upper sublayer T1 or T3, i.e. the condition n2>n1 and n2>n3must be fulfilled. However, refractive-index ratios deviating from thisare also conceivable.

In the example, the rectangular-shaped channel of the sublayer 2functions as an optical conductor.

FIG. 5 shows a block diagram of an add/drop multiplexer. Here, awavelength division multiplex signal WDM is fed to the input E. Thissignal consists of a plurality of independent optical signals which aretransported on differing wavelengths.

In the add/drop multiplexer, the signal of one wavelength can, dependingon the switching status, be conducted outwardly—to the so-called dropside—and removed from the respective output D1 . . . Dn. In parallelwith this, a signal of an unused or outwardly conducted channel of thewavelength division multiplex signal can be added. This occurs on theadd side at the respective input A1 . . . An.

After a channel has been dropped or added, a correspondingly changedwavelength division multiplex signal WDM is emitted at output Z.

FIG. 6 shows the basic internal structure of such an add-dropmultiplexer according to FIG. 5.

The wavelength division multiplex signal WDM is firstly fed to ademultiplexer DEMUX. This divides the fed signal in accordance with thenumber of channels into a plurality of subsignals. One channel is shownin the representation. This subsignal is fed to a first optical filterFI1 which forwards a filtered signal to an add/drop device ADE. Thisdevice can be fashioned for example as a micro-electrical-mechanicalsystem, MEMS for short. The decoupled or coupled signal can optionallybe amplified by means of the amplifiers V1 and V2 and is fed via asecond filter FI2 to the multiplexer MUX which combines it with theother channels, not shown, to form a new multiplex signal WDM.

This arrangement is usually constructed discretely. It canadvantageously be integrated by using the printed circuit boardaccording to the invention. Here, the demultiplexers, filters,micro-electrical-mechanical systems, amplifiers and multiplexers can beintegrated on a printed circuit board together with the controlelectronics or further-processing electronics.

The need for time-consuming splicings, etc. is avoided in this way andthe overall arrangement is more compact and more cost-effective.

As electro-optical, opto-electrical or optical means covering passiveand active functions and constructed on organic and/or inorganicmaterials, micro-electrical-mechanical systems, MEMS for short, cancomprise optical filters such as gain flatness filters and tilt filters,optical switches, optical amplifiers such as fiber amplifiers orsemiconductor laser amplifiers doped with erbium or other rare earths,laser diodes, photodiodes, arrayed waveguide gratings (AWGs for short),branches or taps, optical modulators such as Mach-Zehnder modulators orelectro-absorption modulators, and other means of this kind.

By integrating electro-optical means such as for example laser diodes,refractive-index-changing components, optical amplifiers, opticalswitches and opto-electrical means such as for example photodiodes intothe printed circuit board, i.e. passive, such as switching andattenuating, and active, such as amplifying, non-linear effects andfunctions, a compact and cost-effective structure is attained. Here,inorganic and organic materials can advantageously be combined in orderto obtain desired optical or electrical properties.

For example, polymer can be used in place of glass, silicon oxide orsilicon dioxide for the optical conductor paths.

Optical amplifiers such as for example erbium-doped fiber amplifiers,EDFA for short, erbium-doped waveguide amplifiers, EDWA for short,semiconductor laser amplifiers or semiconductor optical amplifiers, SOAfor short, consist of a plurality of components such as monitorphotodiodes, pump lasers, filters and fiber splices. Optical amplifierscan advantageously be integrated by using the printed circuit boardaccording to the invention.

The multilayer printed circuit board is manufactured with optical andelectrical layers. Optical waveguides and suitable optical switches,such as MEMS, which enable a coupling and decoupling of the opticalsignal are incorporated in the optical layers which consist of thinglass or polymers and where applicable are doped, for example witherbium. Input and output optical signals can be fed to a fiber connectoror connector strip which is arranged in, on or near the printed circuitboard. The electrical and optical contacts or connecting elements of theprinted circuit board can be combined or fashioned individually.

Three-dimensional optical structures can also be integrated into theprinted circuit board.

With the printed circuit board, the optical signal can be forwarded fromone layer to another layer and supply various means, devices orcomponents.

Various optical signals can be bundled or separated in integratedmultiplexers, demultiplexers, splitters and tap-couplers. In the opticallayer, optical amplifiers which balance losses and effect an adjustmentof the light signal can be achieved through doping.

In addition to the previous functions the electrical layers take overthe power supply and the monitoring and control of the electrical,electronic, electro-optical, opto-electrical and optical devices.

The hybrid construction of circuits, flipchip assembly or otherconnection technologies are possible in order to integrate devices.

The printed circuit boards according to the invention can be used notonly in data communications and telecommunications engineering but alsofor example in automotive engineering, medical technology, power-stationengineering, etc.

The advantages mentioned and the advantages resulting from opticalintegration include, beside the reduction of overall dimensions and theimproved repetition accuracies in production, the following.

An integrated solution in the circuit holder or the printed circuitboard is possible in the place of individual components. An integratedarrangement generally needs smaller electrical field dimensions,therefore less energy, which in turn means fewer disruptions such asthrough electromagnetic incompatibility, EMI for short.

The major outlay in terms of working time required for the precisepositioning of fiberoptic modules and the associated costs are minimizedby the integration according to the invention, as fiber splices are nolonger necessary.

A printed circuit board can contain a complete optical add/dropmultiplexer.

A facility has been created for cost-effective production, control andintegration of optical switches.

1-8. (canceled)
 9. An electrically controlled optical add-dropmultiplexer, comprising: a multiplexer; a demultiplexer; an opticalfilter; a micro-electrical-mechanical system; and an optical amplifier,wherein the multiplexer, the demultiplexer the optical filter, themicro-electrical-mechanical system and the optical amplifier arearranged on a multilayer printed circuit board comprising at least oneelectrically insulating layer, at least one electrically conductiveconductor path on an upper surface of the at least one electricallyinsulating layer to which the optical add-drop multiplexer iselectrically connected, at least one optical layer beneath the at leastone electrically insulating layer, a connecting opening formed withinthe at least one optical layer, an optical coupling element within theconnecting opening whereby the optical add-drop multiplexer is orientedabove the optical coupling element so that an optical signal exiting theoptical add-drop multiplexer is redirected by the optical couplingelement to an optical waveguide formed within the at least one opticallayer.
 10. The add-drop multiplexer according to claim 9, wherein alayer of the multilayer printed circuit board has both optical andelectrical conductor paths.
 11. The add-drop multiplexer according toclaim 9, wherein the multilayer printed circuit board has organic andinorganic materials.
 12. The add-drop multiplexer according to claim 9,wherein the multilayer printed circuit board has organic or inorganicmaterials.
 13. The add-drop multiplexer according to claim 9, theoptical conductor paths are made of glass and polymers.
 14. The add-dropmultiplexer according to claim 9, the optical conductor paths are madeof glass or polymers.
 15. The add-drop multiplexer according to claim 9,wherein the optical conductor paths are fashioned from an element fromthe group consisting of: glass, silicon oxide, silicon dioxide, andpolymer.
 16. The add-drop multiplexer according to claim 9, wherein theoptical conductor paths have three-dimensional optical structures suchthat two optical conductor paths arranged in different layers of themultilayer printed circuit board are connected to one another.
 17. Theadd-drop multiplexer according to claim 9, the optical conductor pathscontain a doping.
 18. The add-drop multiplexer according to claim 9,wherein the add-drop multiplexer further comprises; an electro-opticaldevice, an opto-electrical device, and an optical device.
 19. Anelectrically controlled electro-optical device comprising: an opticalside connected optically to an optical coupling element positionedwithin a connecting opening formed within an optical layer of amulti-layer printed circuit board, the electro-optical device beingelectrically connected with at least one electrically conductive pathformed on an electrically insulting layer of the multi-layer printedcircuit board positioned above the optical layer whereby an opticalsignal exiting the electro-optical device is redirected substantiallyorthogonally by the optical coupling element to an optical waveguideformed within the optical layer of the multi-layer printed circuitboard.